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                                        Vitamin K

Vitamin K is a fat-soluble vitamin.

Naturally occurring forms of vitamin K include phylloquinone (vitamin K1) and a family of molecules called menaquinones (MKs or vitamin K2)

With limited vitamin K storage capacity, the body recycles vitamin K in the vitamin K oxidation-reduction cycle in order to reuse it multiple times. (More information)

Vitamin K is the essential cofactor for the carboxylation of glutamic acid residues in many vitamin K-dependent proteins (VKDPs) that are involved in blood coagulation, bone metabolism, prevention of vessel mineralization, and regulation of various cellular functions.

Where is it found:

Vitamin K1 is obtained from leafy greens and some other vegetables. Vitamin K2 is a group of compounds largely obtained from meats, cheeses, and eggs, and synthesized by bacteria.


Vitamin K deficiency is only considered clinically relevant when prothrombin time increases significantly due to a decrease in the prothrombin activity of blood . Thus, bleeding and hemorrhage are the classic signs of vitamin K deficiency, although these effects occur only in severe cases. Because vitamin K is required for the carboxylation of osteocalcin in bone, vitamin K deficiency could also reduce bone mineralization and contribute to osteoporosis .

Vitamin K deficiency can occur during the first few weeks of infancy due to low placental transfer of phylloquinone, low clotting factor levels, and low vitamin K content of breast milk . Clinically significant vitamin K deficiency in adults is very rare and is usually limited to people with malabsorption disorders or those taking drugs that interfere with vitamin K metabolism. In healthy people consuming a varied diet, achieving a vitamin K intake low enough to alter standard clinical measures of blood coagulation is almost impossible.

The following groups are among those most likely to have inadequate vitamin K status.

Newborns not treated with vitamin K at birth.

Vitamin K transport across the placenta is poor, increasing the risk of vitamin K deficiency in newborn babies. During the first few weeks of life, vitamin K deficiency can cause vitamin K deficiency bleeding (VKDB), a condition formerly known as “classic hemorrhagic disease of the newborn.” VKDB is associated with bleeding in the umbilicus, gastrointestinal tract, skin, nose, or other sites  VKDB is known as “early VKDB” when it occurs in the first week of life. “Late VKDB” occurs at ages 2–12 weeks, especially in exclusively breastfed infants due to the low vitamin K content of breast milk or in infants with malabsorption problems (such as cholestatic jaundice or cystic fibrosis) [7]. VKDB, especially late VKDB, can also be manifested as sudden intracranial bleeding, which has a high mortality rate . To prevent VKDB, the American Academy of Pediatrics recommends the administration of a single, intramuscular dose of 0.5 to 1 milligram (mg) vitamin K1 at birth.

People with malabsorption disorders

People with malabsorption syndromes and other gastrointestinal disorders, such as cystic fibrosis, celiac disease, ulcerative colitis, and short bowel syndrome, might not absorb vitamin K properly. Vitamin K status can also be low in patients who have undergone bariatric surgery, although clinical signs may not be present . These individuals might need monitoring of vitamin K status and, in some cases, vitamin K supplementation.


he two forms of vitamin K (vitamin K1 and vitamin K2) are LIKELY SAFE for most people when taken by mouth or injected into the vein appropriately. Most people do not experience any side effects when taking in the recommended amount each day.

Special Precautions & Warnings:

Pregnancy and breast-feeding: When taken in the recommended amount each day, vitamin K is considered safe for pregnant and breast-feeding women. Don't use higher amounts without the advice of your healthcare professional.

Children: The form of vitamin K known as vitamin K1 is LIKELY SAFE for children when taken by mouth or injected into the body appropriately.

Diabetes: The form of vitamin K known as vitamin K1 might lower blood sugar levels. If you have diabetes and take vitamin K1, monitor your blood sugar levels closely.

Kidney disease: Too much vitamin K can be harmful if you are receiving dialysis treatments due to kidney disease.

Liver disease: Vitamin K is not effective for treating clotting problems caused by severe liver disease. In fact, high doses of vitamin K can make clotting problems worse in these people.

Reduced bile secretion: People with decreased bile secretion who are taking vitamin K might need to take supplemental bile salts along with vitamin K to ensure vitamin K absorption.

Warfarin (Coumadin) interacts with VITAMIN K

Vitamin K is used by the body to help blood clot. Warfarin (Coumadin) is used to slow blood clotting. By helping the blood clot, vitamin K might decrease the effectiveness of warfarin (Coumadin). Be sure to have your blood checked regularly. The dose of your warfarin (Coumadin) might need to be changed.